As a memory element or a nonvolatile switching element for a programmable logic that is capable of changing a circuit structure of a semiconductor device, a variable resistance element using metal ion migration in an ion conducting material (an solid of which an ion can freely move around in an interior) and an electrochemical reaction is disclosed (Non-Patent Document 1). This variable resistance element has a three-layered structure having a first electrode 11 capable of supplying a metal ion, an ion conducting layer 20 in which the metal ion can conduct and a second electrode 12 which is less ionizable than the first electrode 11, as schematically illustrated FIG. 1.
In the variable resistance element disclosed in Non-Patent Document 1, a copper ion is used as the metal ion, copper is used as the first electrode 11 which serves as a source of supply for the copper ion, a metal oxide layer such as tantalum oxide is used as the ion conducting layer 20, and platinum is used as the second electrode 12 which is less ionizable. The variable resistance element using the electrochemical reaction has characteristics of a small size and a large ratio of resistance between an on state and an off state.
FIG. 2A shows a schematic diagram illustrating an operation of the variable resistance element and FIG. 2B shows a current-voltage graph. The above variable resistance element is in an off state that has high resistance just after the manufacturing. For transition from the off state to an on state that has low resistance, as illustrated in (a) of FIGS. 2A and 2B, the first electrode 11 is connected to the ground, negative voltage is applied to the second electrode 12, and metal ions are generated from the metal of the first electrode 11 by the electrochemical reaction and dissolved in the ion conducting layer 20. The metal ions 13 in the ion conducting layer 20 is precipitated as a metal on the surface of the second electrode 12. As illustrated in (b) of FIGS. 2A and 2B, the precipitated metal forms a metal bridge between the first electrode 11 and the second electrode 12 and electrically connects the first electrode 11 with the second electrode 12 (makes the transition to the on state). On the other hand, for transition from the on state to the off state, as illustrated in (c) of FIGS. 2A and 2B, the first electrode 11 is connected to the ground, and positive voltage is applied to the second electrode 12. As illustrated in (d) of FIGS. 2A and 2B, this breaks a part of the metal bridge and makes the transition to the off state.
Patent Document 1:    Japanese Patent Kokai Publication No. JP2006-319028A
Non-Patent Document 1:    Shunichi Kaeriyama et al., “A Nonvolatile Programmable Solid-Electrolyte Nanometer Switch”, IEEE Journal of Solid-State Circuits, Vol. 40, No. 1, pp. 168-176, January 2005.
Non-Patent Document 2:    Toshitsugu Sakamoto et al., “Nonvolatile solid-electrolyte switch embedded into Cu interconnect”, 2009 Symposium on VLSI Technology Digest of Technical Papers, pp. 130-131, 2009.